Such a device, used in a microwave system, serves in particular in the event of malfunction to dissipate the non-active energy of the system in the form of heat, and in particular the energy carried in a microwave transmission line.
Such a microwave transmission line can be constituted by a dielectric substrate having one face carrying a conductive strip and its opposite face carrying a metal ground area, the conductive strip being connected to a resistive layer deposited on the substrate.
Such a transmission line is generally referred to as a “microstrip”.
The impedance of such a microwave transmission line is generally 50 ohms (Ω).
The device forming a resistive load can be housed in a package connected to the system by a cable, thus enabling the device to be put into contact with a cooling radiator. Such a device is commonly referred to as an offset load.
In a variant, the device may be fixed directly onto a piece of equipment of the system, e.g. a circuit thereof.
Patent No. EP 0 092 137 describes a device forming a resistive load that comprises an insulating substrate having deposited thereon adjacent resistive layers in the form of circular sectors. The outer arc of a resistive layer constitutes the input of the device and the inner arc its output. That device seeks to enable heat power to be dissipated more uniformly and to a greater extent.
French patent application No. FR 2 486 720 describes a device for terminating a microwave transmission line, the device comprising a dielectric substrate with a resistive layer constituting a terminating load on one face. The resistive layer may present a trapezoidal shape with its major base constituting the input for the microwave transmission line and with its minor base being connected to ground metallization. A transverse conducive strip may be deposited on the resistive layer in contact with the conductive strip and interconnecting two metallizations that are to co-operate with a ground plane to form two capacitors.
U.S. Pat. No. 6,326,862 describes an electrical termination system comprising a package having a dielectric substrate supporting a termination circuit element located therein. The package has a first cavity that is relatively tall, above the junction between the inner conductor of the coaxial cable and the dielectric substrate. This first cavity opens out into a second cavity of smaller height. The double cavity is intended to correct impedance mismatches.